The inventive concepts relate to semiconductor memory devices.
Semiconductor devices have been highly integrated to provide increased performance and reduced manufacturing costs. Integration densities of semiconductor devices may directly affect the costs of the semiconductor devices. An integration density of a two-dimensional (2D) or planar semiconductor memory device may be mainly determined by an area of a unit memory cell. Thus, the integration density of the 2D semiconductor memory device may be greatly affected by a technique of forming fine patterns. However, since extremely high-priced apparatuses are needed to form very fine patterns, the integration density of 2D semiconductor memory devices may continue to increase but may be still limited. Thus, semiconductor memory devices including three-dimensionally arranged memory cells have been developed.